1. Technical Field
The present invention involves sheet-feeding devices that deliver sheets stacked on a sheet feeding tray to a predetermined position, and in particular relates to sheet feeding devices furnished with a tilting tray free to rise/lower in order to bring sheets into pressure-contact with delivery means.
2. Description of the Related Art
In sheet feeding devices provided in image-capturing apparatuses, copiers, or the like, to convey sheets to a predetermined image-capturing position, it is known to dispose the sheet discharging tray below the sheet feeding tray, and to form in the shape of a U the conveying path along which sheets on the sheet feeding tray are conveyed to the sheet discharging tray via the image-capturing position. In this type of sheet feeding device, the sheet feeding tray is pivotable upward so as to take a sheet out from the sheet feeding tray or to remove a sheet jammed in a sheet discharging section.
Meanwhile, a sheet feeding device capable of handling a large number of sheets at a time has been desired. A known feeding device of this type adopts a sheet feeding tray unit composed of a sheet feeding tray that supports the trailing end of a sheet, and a tilting tray free to rise/lower to support a leading end of the sheet (for example, Japanese Unexamined Pat. App. Pub. No. 2003-118851).
The sheet feeding tray unit, composed of the sheet feeding tray and the tilting tray, uses an elevating mechanism including an elevating lever and a driving motor for the elevating lever in order to raise and lower the tilting tray. The elevating mechanism is provided behind the tilting tray. The tilting tray is pivotably supported by the sheet feeding tray at one end and is free at the other end. The elevating lever pushes up the rear side of the tilting tray to raise the tilting tray. The driving motor is reversely rotated to allow the elevating lever to pivot away from the rear surface of the tilting tray, whereby the tilting tray lowers under its own weight.
The system just described controls the tilting tray by receiving a sheet-feeding-command signal from the image-capturing apparatus and actuating the elevating lever to raise the tilting tray from a setting position where sheets are set into place on the tilting tray, to a delivery position where the uppermost one of the sheets abuts against a delivery roller.
However, in the conventional sheet feeding device, the elevating mechanism is fitted integrally to the sheet feeding tray unit. Thus, when the sheet feeding tray unit is to be pivoted, the weight of the elevating mechanism acting on the sheet feeding unit may distort the tray, the pivoting operation might not be able to take place smoothly, or shock on the sheet feeding tray unit when pivoting may occur. The adverse influence of the elevating mechanism's weight has made handling the tray unit challenging.
A sheet feeding device that has been proposed to address this problem has an elevating mechanism made up pf an elevating lever, a driving motor, and associated components, and provided in the main body of the device, the elevating lever having a leading end extending to below the tilting tray (for example, Japanese Unexamined Pat. App. Pub. No. 2001-139162). This configuration resolves the above-described problem because the sheet feeding tray unit is separate from the elevating mechanism.
However, when the sheet feeding tray is swung upward while the tilting tray is rising by being pushed up along the rear surface of the elevating lever, the tilting tray is supported on the sheet feeding tray only at one end and is free at the other end. Furthermore, the elevating lever is exposed from a device cover. Consequently, when the sheet feeding unit is returned to the sheet setting position, there is a chance that the tilting tray may go in underneath the elevating lever. A further danger is that the leading end of the tilting tray may knock against the elevating lever.
Moreover, when the sheet feeding unit is swung, the other, free end of the tilting tray pivots freely, colliding against the sheet feeding tray or other components and making noise. A further problem therein is that the components may be damaged.